import java.util.Scanner;

public class Test {

    //斐波那契数列
    public static int fib(int n){
        if(n <= 0){
            return -1;
        }else if(n == 1 && n == 2){
            return 1;
        }
        return fib(n-1) + fib(n-2);
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        while(scanner.hasNextInt()){
            int n = scanner.nextInt();
            int ret = fib(n);
            System.out.println(ret);
        }
    }
}
